Windows Character Encoding Fix for AI Agents

Fix garbled Chinese/Unicode text output when running AI agents on Windows through POSIX-compatible shells.

Problem

When AI agents run commands on Windows through POSIX shells (Git Bash, MSYS2, BusyBox, or any Unix-like shell layer), text output containing Chinese or extended Unicode characters often appears garbled:

$ python3 -c "print('中文测试')"
���IJ���  ← garbled
$ echo "中文测试"
中文测试       ← correct

Root Cause